July 3 (UPI) — The Justice Department on Friday called on states to investigate whether businesses and individuals are artificially inflating gas prices amid complaints from President Donald Trump that costs are too high.

Associate Attorney General Stanley Woodward Jr. along with Federal Trade Commission Chairman Andrew Ferguson sent a letter to state attorneys general asking them to join federal investigators in probing potentially illegal practices.

“Recent volatility in crude oil prices does not suspend either the antitrust laws or state consumer protection laws, and it does not authorize companies to manipulate retail prices or collude with their competitors,” the letter read.

“We also encourage State Attorneys General to use all tools available under your state laws to investigate and prosecute any misconduct causing unjustified prices increases — particularly conduct that violates state antitrust and consumer protection statutes.”

Gas prices have been on the rise since late February when the United States and Israel began attacks on Iran. Tehran, in return, largely shut down the Strait of Hormuz to traffic, crippling the the transport of oil through the waterway. About one-fifth of the world’s gas supplies pass through the strait.

An agreement between the United States and Iran reopened the strait, but Trump took to Truth Social on June 23 to complain that gas prices had not dropped fast enough.

“The big Oil Companies are not dropping their price at the pump commensurate with the sharply lower prices they are paying for Oil,” he wrote. “Those prices are dropping like a rock! In other words, customers are being ‘gouged.’

“I have instructed the DOJ to immediately start looking into this. Gasoline prices better start going down a lot faster than what I’m seeing!”

AAA reported Friday that the current national average gas price was $3.82 per gallon for regular gasoline, down from $4.26 a month prior. One year ago, it was $3.16 per gallon.